Filter assemblies for air conditioning and heating equipment have conventionally been formed of a core of glass fibers bound together by small particles of resinous binders. The glass fibers were usually coated with a thin film of a viscous non-volatile oil to capture particles from the air moving through the fibers. The glass fiber core of such a filter assembly is installed in a thin rectangular paperboard box. The box has opposite walls which are perforated to allow air to flow through the glass fiber core. Although commercially successful, such a filter assembly is not nestable or stackable due to its box-like structure. This structure presents problems in storage and shipment of such filter assemblies because even though the package units are light in weight, their volume makes them expensive to ship where shipping costs are based on volume as well as weight. Also, their volume makes storage costs expensive.
Filter assemblies that can be nested and stacked are shown in U.S. Pat. Nos. 3,830,045 and 3,970,440. These filter assemblies utilize a frame formed of a cut and scored blank of paperboard. When assembled, the paperboard blank forms planar frame members which engage a substantially sheet form filter element. The frame members are flared outwardly to permit the frames to be nested inside one another. Commercially available filters made in accordance with the teachings of these patents are nestable but these filters lack rigidity and strength.
This invention is directed to an easily manufactured filter frame and filter assembly which can be stacked and nested to conserve space and which is sufficiently rigid to function without excessive vibration or breakage.
An object of this invention is a frame for a filter assembly that can be molded in a single integral piece.
Another object is a filter assembly frame that can be manufactured from readily available and inexpensive material, specifically reprocessed paper pulp.
Another object is a filter assembly that uses less filter media than similar sized filter assemblies formed of cut and folded paperboard or cardboard box structures.
Other objects will be found in the following specification, claims and drawings.